Adhesive label with water-based release coating

ABSTRACT

An adhesive label with a water-based release coating and methods for applying the water-based release coating to the adhesive label are provided. The water-based release coating is a non-silicon based formulation having a fluorochemical. The water-based release coating can be applied in a single-pass process or a double-pass process when manufacturing the adhesive label.

RELATED REFERENCE

The present application is a non-provisional of and claims priority toU.S. Provisional No. 61/914,213, entitled “Adhesive Label withWater-Based Release Coating,” filed on Dec. 10, 2013; the disclosure ofwhich is incorporated by reference herein in its entirety.

BACKGROUND

The ubiquitous adhesive label is available in a myriad of configurationsfor use in various applications, including specialty applications. Thetypical an adhesive label includes pressure-sensitive adhesive on itsback side and initially laminated to an underlying release liner. Therelease liner typically has a release coating to provide a weak bondwith the adhesive for permitting the individual removal of labels fromthe liner when desired.

Adhesive labels may be found in individual sheets, or joined together ina fan-fold stack, or in a continuous roll. Label rolls are typicallyused in commercial applications requiring high volume use of labels.

One type of label roll may be in the form of a web and does not includea liner sheet. Such label rolls are known as linerless label rolls. Thelabels may be formed of thermal paper for sequential printing ofindividual labels in a direct thermal printer. Or, a thermal transferprinter may also be used. The front surface of the label web may becoated with a release coating. In the fast food industry, linerlesslabels may be used in identifying individual food products in typicalsales transactions.

A preferred release coating for use with all types of adhesive labels issilicone. However, silicone is perceived to be environmentallyunfriendly.

Therefore, it would be desirable to provide an adhesive label with analternative release coating than silicone.

SUMMARY

In various embodiments, an adhesive label and non-silicon based releasecoating and methods of applying the non-silicon based release coatingare provided.

An example adhesive label includes a substrate, an adhesive on a firstsurface of the substrate, and a water-based release coating applied to asecond surface of the substrate with a formulation including afluorochemical.

The substrate can be paper, such as a base paper, a single layer coatedpaper, a several layer coated paper, a thermal coated paper, a topcoated paper (over the thermal coating), film, or any other substratethat can receive coated layers.

The fluorochemical can be coated directly onto the substrate, mixed intoa body of release coatings, or as a component in a mixture containingone or more of the following chemicals: starch, polyvinyl alcohol(PVOH), polyvinyl acetate (PVA), sizing agent, clay, silica,precipitated calcium carbonate (PCC), thickener, and rheology modifier.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view of a thermal printer dispensing pressure sensitivelabels having a release coating, according to an embodiment.

FIG. 2 is a cross-sectional view of a linerless label, according to anembodiment.

FIG. 3 is a view of a second surface of the linerless label of FIG. 2,including printed text, according to an embodiment.

FIG. 4 is a view of a first surface of the linerless label of FIG. 2,including a strip of activated adhesive, according to an embodiment.

FIG. 5 is an example apparatus for applying a release coating, accordingto an example embodiment.

FIG. 6 is an example double-sided thermal printer for printing labelshaving a release coating, according to an embodiment.

DETAILED DESCRIPTION

FIG. 1 is a view of a thermal printer dispensing pressure sensitivelabels having a release coating, according to an embodiment. Withreference to FIG. 1, a printer 10 configured for printing in sequenceindividual labels 12 for use in a typical fast food application. Forexample, food may be placed in a suitable food package 14 such as thepaper box illustrated, or simple wrapping paper. Printer 10 may includea thermal printer, such as a single or double-sided thermal printer (asshown in the FIG. 6).

Print or identifying indicia 16 is printed on a label 12 in printer 10for identifying the contents of the package, for example. The individualprinted label 12 may then be removed from printer 10 and applied usingthe adhesive 38 to the food package 14 as illustrated in the a method(12 printed from 10 to 16 to APPLY LABEL to 12 applied to 14 using 38(adhesive patch), which is shown in FIG. 1.

FIGS. 2-4 illustrate an example linerless label 100 that includes aprintable surface including imaging material on one side and aheat-activated adhesive surface on the other side having a releasecoating, according to embodiments of the invention. It is to be notedthat other types of labels are also envisioned.

FIG. 2 is a cross-sectional view of a linerless label having a releasecoating, according to an embodiment.

With reference to FIG. 2, linerless label 100 is formed of layersincluding a substrate 102, a thermal print layer 104, a heat-activatedadhesive layer 106, and a release coating 108. The adhesive layer 106overlies a first surface 112 of the substrate 102 and the print layer104 overlies a second surface 114 of the substrate 102 of the printlayer 104. The release coating 108 overlies surface 116 of the printlayer 104.

In some embodiments, substrates may be thermally resistant in order toprevent heat applied to one side of the substrate from activatingmaterials on the other side of the substrate.

Linerless label 100 may be wound into a roll. The adhesive layer 106comes into contact with the release coating 108, thereby minimizingadhesion between the adhesive layer 106 and the print layer 104 orunderlying substrate 102.

The print layer 104 can include one or more layers of thermal imagingmaterial. For instance, the print layer 104 can include a thermaltransfer receptive coating suitable for thermal transfer printing.Alternately or additionally, the print layer 104 may include one or morethermally sensitive coatings which are adapted to change color uponapplication of heat thereto by which direct thermal printing isprovided.

The adhesive layer 106 may include water based adhesives and may beapplied in patches using a printing press.

As an alternative to using a separate print layer 104, substrate 102could comprise thermochromic paper. A thermal print head can printvisible patterns on thermochromic paper without requiring an additionalprint layer to be formed on the substrate.

FIG. 3 is a view of a second surface of the linerless label of the FIG.2, including an example printed or imaged text, according to anembodiment.

That is, FIG. 3 illustrates an example of a second surface 202 of thelinerless label 100 after printing. In this example, the label 100 is areceipt for a fast food meal. As shown in FIG. 2, the second surface 202of the linerless label 100 has been printed with transaction informationby, for example, direct thermal printing of one or more thermallysensitive compounds in the print layer 104.

FIG. 4 is a view of a first surface of the linerless label of FIG. 2,including a strip of activated adhesive, according to an embodiment.

The first surface 302 includes a wet adhesive portion in the form of atacky strip 310 of heat-activated adhesive material that has beenactivated by, for example, a thermal print head. In this example, thetacky strip 310 can be used to attach the receipt to an associated bagof food. Consequently, the bag and the receipt can be handed to acustomer simultaneously.

The tacky strip 310 can be formed in one of at least two differentmethods. In the first method, the entire first surface 112 of thesubstrate 102 can be overlaid by a heat-activated adhesive that is dryand non-tacky prior to activation. Then, only a selected portion of theheat-activated adhesive, the portion defining the strip 310, isactivated by heat applied with a thermal print head. Depending on theembodiment, such activation may occur at or substantially at the sametime as, or at some time after the second surface 202 of the receipt hasbeen printed with transaction information. In the second method, aportion of the first surface 302 defining the strip 310 can be overlaidwith a heat-activated adhesive that is dry and non-tacky prior to use.The entire heat-activated adhesive can be activated by a thermal printhead, which activation may, depending on the embodiment, occur at orsubstantially at the same time as, or at some time after the secondsurface 202 of the receipt has been printed with transactioninformation. Either manner will result in a tacky adhesive strip 310.When a double-sided thermal printer is used, a first thermal print headcan print on the second surface 202 of the receipt while a secondthermal print head activates the first surface 302 of the receipt.

In the illustrated embodiment, a water-based release coating formulation108 is used, instead of a silicone release coating. Water-based releasecoatings have been designed to be applied in a conventional coater suchas a rod metering or puddle size press, a blade coater or any othercoater capable of spreading the coating uniformly. However, applicationof the release coating is illustrated herein using a press rather than aconventional coater.

It is to be noted that there are significant differences between asilicone coating and the body of release coatings 108 that are beingsuggested as replacement. The silicone is 100% solids and cures withUltraviolet (UV) energy in a short period of time. The body of availablerelease coatings 108 has low percentage solids (in the range of 35% to45%) and low viscosity (300 to 500 cps). Low solids need longer dryingtime at higher temperature. However, thermal paper cannot run at hightemperature because the heat will pre-activate the thermal layer. Dryingat low temperature using a water-based coating requires longer dwelltime.

The water-based replacement release coating 108 is chosen from a body ofrelease coatings. There have been several challenges to obtain a smoothand uniform coating layer applied on a substrate, where the substratecan be paper, such as a base paper, a single layer coated paper, aseveral layer coated paper, a thermal coated paper, a top coated paper(over the thermal coating), high temperature thermally coated paper,film, or any other substrate that can receive coated layer. Thechallenges have been exacerbated because of the thermal print layer onthe substrate, which cannot be exposed to high temperatures. If thethermal print layer is heated above the activating temperature of thesubstrate, the thermal print layer will pre-image. The temperature rangeto dry this coating has to be carefully selected to be high enough todry and cure the release coating 108 and low enough not to pre-image thethermal print layer. The challenge is that if the release coating 108 isstill damp when the water-based adhesive is applied, both of these willcome into contact with each other and this interaction will cause strongcovalent bonds to form. The transfer of the wet adhesive to the surfaceof the wet release coating 108 causes contamination and renders both theadhesive and the release coating 108 ineffective. The adhesive may stickto the thermal print layer and can either remove the thermal print layeror rip the substrate if the adhesive-paper bond is too strong. As aresult, the adhesive losses tack due to adhesive transfer to thesubstrate and the thermal print layer.

From a body of water-based release coatings such as grease resistantchemicals, more specific fluorochemicals (FC) are selected to chemicallymodify the release coating and meet the above challenges. The FC iswater miscible and has a C-6 backbone. The chosen FC contains ahydrophilic and a hydrophobic tail.

FC can either be applied alone or in a coating formulation. Whetherapplied by itself or in the release coating formulation, the hydrophilictail is anchored into the wet release coating or the underlyingsubstrate while the hydrophobic tail remains outside the releasecoating, lining up to resemble a bed of nails and protecting thesubstrate from any liquid (water, oil, etc.) penetration. This FC isuniformly coated on the surface (as it has leveling properties).

Moreover, the FC improves the release coating by reducing the releaseforce from a convention 0.12 lbf to an improved 0.045 lbf.

In addition, the FC also has the added attribute of accelerating thedrying process when added on the surface of the substrate, thermal printlayer coating or additional top coated layer. The FCs is made at around20% solids, has the viscosity of water (1 g/cc) and is mixed in therelease coating at 5 to 10 wet lb/ton of paper. The mixture of FC in therelease coating (coating formulation) needs to be dried in aconventional dryer rather than with UV energy (used for silicone) andthe temperature varies according to the coat weight of the releasecoating formulation. However, it is to be noted that when the substrateis a high-temperature thermally coated paper, the temperatures can beincreased and correspondingly the high end range of temperatures listedin Table 1 can be increased to accelerate the drying times. Thetemperature ranges for the release coating formulation are based on thecoat weight and percentage solids and are given in Table 1 below

TABLE 1 Dryer Temperature Range for the Coating Formulation DryerTemperature Range for Coating Formulation T1 T2 T3 220 230 240 210 220230 200 220 220 190 200 210 190 200 200 180 180 190 170 170 180 150 150150

In one example application, the FC is added to the surface of thesubstrate. The FC can be coated directly onto the substrate, mixed intoa body of release coatings, or as a component in a mixture containingone or more of the following chemicals: starch, polyvinyl alcohol(PVOH), polyvinyl acetate (PVA), sizing agent, clay, silica,precipitated calcium carbonate (PCC), thickener, and rheology modifier.

In an embodiment, the FC is mixed with just starch and coated directlyonto the substrate.

In an embodiment, the FC is UNIDYNE TG-8151 distributed by Daikin,Industries, LTD.

The substrate can be paper, such as a base paper, a single layer coatedpaper, a several layer coated paper, a thermal coated paper, a topcoated paper (over the thermal coating), film, or any other substratethat can receive coated layers.

Trials have shown that if the adhesive is applied within 24 hours ofwhen the release coating was applied, the adhesive peels off whenunwinding the linerless roll of labels. This is due to the interactionof the wet adhesive and wet release coating formulation duringmanufacturing. By adding the chosen FC to the coating formulation, aboundary layer is formed between the release coating formulation(containing the FC) and the adhesive. The wet release coatingformulation with the FC's hydrophobic tails lining up on the surface ofthe release coating formulation serves as a barrier between the wetadhesive and the moist release coating formulation. The FC tails willrepel the adhesive's liquid preventing it from penetrating into therelease coating mixture. As both the release coating layer and adhesivedry, the hydrophilic side of the FC will migrate to the surface and willlay horizontally on the surface of the release coating protecting therelease coating layer. The chosen FC will also accelerate the dryingprocess. When the release coating formulation is dried, it will not onlyact as an adhesive barrier, but will also impart moisture, oil, andgrease resistance protecting the linerless label from moisture andgrease and oil stains.

In order to apply the example water-based release coating, one examplemethod includes:

-   -   1. Using suitable anilox rolls to deliver between 1 and 8 wet        gsm of release coating material. The anilox rolls capable of        carrying this amount of liquid are in the range of 300 PLI/8.0        BCM and 400 PLI/6.5 BCM.    -   2. Drying all the excess water in the release coating, including        running at much higher temperature without imaging the thermal        coating. The drier temperature range is significantly increased        going from the standard temperature range used at present (TO)        to a much higher temperature range (Ti), which will vary        according to the coat weight applied as can be seen in Table 1.    -   3. Changing the release coating application station from the        silicone release coating station.

FIG. 5 is an example apparatus for applying a release coating, accordingto an example embodiment.

An example press 400 is illustrated. The example press is a modifiedflexographic or “flexo” printing press. Modification is necessarybecause flexo presses are normally intended for printing a dot matrix,not applying a uniform release coating. Such presses normally runproducts that have high solids and high viscosity, which dry quickly.The application of a water-based release coating in a normal press isvery challenging because the press has limited drying capacity (dwellingtime based on the speed of the press) and is not designed for waterbased coatings with low solids, which require longer dwell times.

The standard adhesives used at present are at 60% solids and requirehigh coat weight to achieve adequate peel forces ranging from 1 lbf to 3lbf. To achieve high coat weights with low adhesive viscosity between500 to 3,000 cps it is necessary to do a two pass application. However,at high viscosity of around 30,000 cps only one pass application isrequired. Sense marks are also printed during this process and all isdone in a one pass application.

Normally, the release coating would be applied in either of the twoprinting stations or the silicone station. However, the silicone stationhas UV energy which will not dry the water-based coating and neither thefirst nor the second print station has enough drying capacity to dry thecoating. Therefore, in an embodiment, application of the release coatingis moved from the silicone release coating station to the two adhesivestations since both of these have temperature zone driers required todry the low solids water-based release coating. The water evaporationtime of the adhesive should be increased because the adhesive will comeinto direct contact with the release coating.

It is noted, that the silicon station is not used in either the one-passprocess or two-pass process for apply the release coating to the labels.

In an embodiment, of the one-pass process, the release coating is aformulation of the FC and starch.

Table 2 shows the adhesive temperature ranges needed to accelerate thedrying. Since we are using a press to apply release coating rather thana coater, certain modifications have to be made to the process to coatuniformly and dry thoroughly the adhesive.

TABLE 2 Dryer Temperature Range for the Adhesive Dryer Temperature Rangefor T1 T2 T3 205 210 210 180 200 210 170 180 200 170 180 200 160 180 180130 170 170 100 150 150 100 140 140

One or more of the following example modifications can be used toprovide a uniform release coating to be applied on the press in the onepass process.

-   -   1. A radio frequency drier, infra-red drier, or adhesive drier        may be added to print stations 1 or/and 2 to dry the release        coating faster to avoid using the adhesive station and having to        do a second pass on the press, first to add the release coating        and then to add the adhesive.    -   2. A spraying roll may be added to the coating/print station        (such as the first print station in the FIG. 5) to smooth the        release coating out. The spraying roll runs opposite to the        coating roll at a faster speed to smooth the release coating        that has just been printed on the paper. When using a press to        apply release coating, the press prints the release coating on        the substrate using a dot matrix. To obtain a uniform release        coating surface rather than a dot matrix, it is necessary to        smooth the applied release coating with a roll to spread the        release coating uniformly across the press. Its main function is        to level the surface to obtain a uniform release coating surface        layer.    -   3. A pan to catch the release coating formulation may be        installed to prevent pre-wetting of the web. The release coating        formulation has significantly less percentage solids than        required to successfully operate the printer and as a result,        the release coating drips onto the base paper web prior to it        entering the print section where the release coating is applied.        This adds extra moisture to the paper that has to be dried        during the short dwelling time as it travels through the dryer.

Advantageously, this method provides the capability of replacingsilicone with a water-based environmentally friendly release coating,applying the release coating with a press rather than with a coater,preventing wet interaction during drying of the water based adhesive andrelease coating, and preventing blocking/picking due to adhesivepenetration through microscopic cracks in the release coating, andapplying a uniform release coating to seal the surface. If the adhesivecomes into contact when the release coating is wet, the release coatingwill delaminate from the top coat causing picking.

FIG. 6 is an example double-sided thermal printer for printing labelshaving a release coating, according to an embodiment.

An example double-sided thermal printer includes a first print headassembly 510, a second print head assembly 520, and a motor. The firstprint head assembly 510 includes a first print head 550 and a firstplaten 570 rotatable about a first shaft 590. Similarly, the secondprint assembly 520 comprises a second print head 560 and a second platen580 rotatable about a second shaft 600.

During operation of the double-sided thermal printer, the motor drivesthe first and second shafts 590 and 600 to turn the first and secondplatens 570 and 580. Accordingly, when a label 500 is fed into theprinter, rotation of the first and second platens 570 and 580 pushes thelabel 500 in a direction indicated by a vertical arrow. As the label 500passes through the printer, the first and second print heads 550 andselectively heat the two sides of label 500 to perform printingoperations. More particularly, first print head 550 performs printingoperations on a side of label 500 indicated by an arrow 610 and secondprint head 560 performs printing operations a side of label 500indicated by an arrow 620.

In an embodiment, when the applied adhesive is applied to the substrateit can be a pressure-sensitive adhesive. In such a case, pressure can beapplied to the adhesive at a customer's location for the receipt toadhere to customer items, such as, but not limited to: paper/foil wraps,cardboard boxes, clam shells, fries sleeves, cups, etc.

One now appreciates the environmental advantages to a low-solidfluorochemical release coating and other beneficial advantagesenumerated above for such coating.

Furthermore, the release coating taught herein and above has a varietyof other beneficial advantages of as such, but not limited to:

-   -   1. significantly improving print quality of thermally coated        paper (conventional silicon release coatings can cause print        failures);    -   2. writing and printing can be applied on top of the release        coatings taught herein—this is in addition to the print layer        (beneficial for applications, for example, date coding where a        pencil can be used to circle the day of the week, the date, or        any other information);    -   3. improving adherence of the release coating to any preprinted        images that may be on the substrate (for example, silicon does        not interact well with inks such that a paper with a preprinted        logo for a customer or product brand—the release coating        presented herein has no such negative interaction with        preprinted images on the paper; additionally, such a logo or        product brand can be printed after the release layer is applied        (as discussed in 2 above)); and    -   4. improving the curing process of the release coating (for        example, silicon uses UV to cure and UV interferes with        water-based inks so to avoid this UV energy is reduced but a        result of this is that the silicon does not cure properly and        causes picking/blocking issues (UV interferes with sense marks,        typically pre-printed on the same side as the adhesive, after        going through UV, the sense marks show through the front-side        thermal layer—with the release coating herein there is no need        for UV energy so sense marks can be preprinted)).

Although the present invention has been described with particularreference to certain preferred embodiments thereof, variations andmodifications of the present invention can be effected within the spiritand scope of the following claims.

1. An adhesive label comprising: a substrate; an adhesive on at least aportion of a back surface of the substrate; and a water-based releasecoating applied to a front surface of the substrate with a formulationof a fluorochemical.
 2. The adhesive label of claim 1 furthercomprising, a thermal print layer pre-coated to the front surface of thesubstrate before the water-based release coating formulation.
 3. Theadhesive label of claim 1, wherein the water-based release coatingformulation includes starch.
 4. The adhesive label of claim 1, whereinthe water-based release coating formulation includes one or more of:polyvinyl alcohol (PVOH), polyvinyl acetate (PVA), sizing agent, clay,silica, precipitated calcium carbonate (PCC), thickener, and rheologymodifier.
 5. The adhesive label of claim 1, wherein the water-basedrelease coating formulation is cured on the substrate.
 6. The adhesivelabel of claim 1, wherein the water-based release coating formulation isdried on the substrate with one or more of: a conventional dryer, anInfrared dryer, and a microwave dryer.
 7. The adhesive label of claim 6,wherein a drying temperature depends on a coat weight for thewater-based coating formulation.
 8. The adhesive label of claim 7,wherein the drying temperature ranges from about 150° F. to 240° F. 9.The adhesive label of claim 1, wherein the water-based release coatingformulation is applied onto the front surface by a sprayer.
 10. Theadhesive label of claim 1, wherein the water-based release coatingformulation is applied to with a press.
 11. The adhesive label of claim10, wherein the press is anilox rollers.
 12. A method, comprising:applying, by the press, a water-based release coating with a formulationof a fluorochemical on top of a thermal coated layer front surface of asubstrate; and applying, by the press, an adhesive layer to at least aportion of a back surface of the substrate for the adhesive label. 13.The method of claim 12, wherein applying the water-based release coatingfurther includes using anilox rollers to apply the water-based releasecoating with the formulation.
 14. The method of claim 12, whereinapplying the water-based release coating further includes spraying thewater-based release coating with the coating on top of the thermalcoated layer.
 15. The method of claim 12, wherein applying thewater-based release coating further includes using one of: an Infrareddryer, a microwave dryer, and a conventional dryer to dry thewater-based release coating with the formulation at a dryer station ofthe press.
 16. The method of claim 15, wherein applying the adhesivelayer further includes using a convention dryer to dry the adhesivelayer and continue to dry the water-based release coating with theformulation at another dryer station of the press.
 17. The method ofclaim 12 further comprising, feeding, to the press, the adhesive labelin a web of adhesive labels through the press in a single pass to applythe water-based release coating with the formulation and the adhesivelayer.
 18. A method, comprising: applying a water-based release coatingwith a formulation of a fluorochemical on top of a thermal coated layeron a front surface of a substrate; curing the water-based releasecoating with the formulation; and applying an adhesive layer to at leasta portion of a back surface of the substrate.
 19. The method of claim18, wherein the substrate is one of: thermal paper, high-temperaturethermal paper, and a film.
 20. The method of claim 18, wherein applyingthe water-based release coating with the formulation using one of: aroller and a sprayer.